SPOKANE, Wash.  Some experts say global warming is changing wooded regions across the nation, and Northwest timber industry workers are among those following the phenomenon amid concern it could eventually affect their livelihoods.

Glacier National Park is expected to be devoid of its namesake ice formations by 2040, according to U.S. Geological Survey scientists. What's more, the Earth's northern hemisphere has been growing greener over the last two decades as temperatures rise, according to NASA satellite images.

For the region's forests, these changes could have serious consequences, said Steven Running, an ecology professor from the University of Montana who was among speakers who addressed 100 loggers at the Intermountain Logging Conference in Spokane last week. They include increased insect plagues and less snowpack, which acts as a wildfire-prevention blanket.

"This isn't just one or two years of normal variability -- this is a substantial trend over a half century," Running said. "When the old-timers tell you it's not as tough as it used to be, they're not kidding."

Some disagree that global warming is behind the rise of disease, insects and catastrophic wildfires in U.S. forests, said Jim Petersen, founder and editor of Evergreen magazine, a leading forestry publication. But loggers don't want to be left out of the discussion, Petersen said.

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"They're very interested in it. They want to know how it's going to affect their lives and communities," he said. "This is no longer a discussion just between scientists."

The rapid changes in Western forests are difficult to deny, said Ed Shepard, assistant director of the U.S. Bureau of Land Management and another speaker at the event. But he said he thinks increases in insects and fires are due to a century of fire suppression. The ratio of tree species in Idaho forests has been altered dramatically by fire prevention, he said, citing a 1995 University of Idaho study.

"What matters is: How are we going to adjust our forest-management practices?" Shepard told the loggers.

There's very little debate in Canada about warmer winters, drier summers and how they may be affecting forests, said Greg McKinnon, a Canadian Forest Service scientist who directs a national research effort on climate impacts on forests.

In Edmonton, Alberta, where McKinnon works, aspen leaves are emerging three weeks earlier than a century ago, he said.

In British Columbia, 17 million acres were chewed up last year by mountain pine beetles. Beetle populations are growing exponentially because they no longer are being kept in check by low temperatures, McKinnon said.

The Canadian government believes the insects may establish themselves east of the Rocky Mountains, where they quickly could eat their way through the continent's vast boreal forest, McKinnon said.

"There's no speculation," he told loggers. "We're into uncharted territory. Not only are we not getting it under control, but the rate of increase is increasing."